Converting leakage current to DC output

ABSTRACT

A power source capable of supplying power to operate electronics of a system is disclosed. In one example, the power source takes advantage of an electrical potential difference between primary and secondary grounds. The power source can reduce system cost and power consumption.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/958,254, filed on Dec. 1, 2010, and titled “CONVERTING LEAKAGECURRENT TO DC OUTPUT” the entire disclosure of which is incorporated byreference.

BACKGROUND

Consumer and commercial electronic systems may be operated at lowerlevel direct current (DC) voltages (e.g., 5 volts DC). The lower levelDC voltage may be provided to a microcontroller and other electroniccomponents within the electronic system via a switching power supply.However, in some electronic systems a second or auxiliary voltage may beused for electronic components of the electronic system that operate ata voltage that is different than the output voltage of the switchingpower supply.

SUMMARY

The inventors herein have developed a method for supplying primary andsecondary power sources, the method comprising: producing a firstvoltage via a transformer, the transformer including a primary groundelectrically and a secondary ground; and producing a regulated secondvoltage via a potential difference between the primary ground and thesecondary ground.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example electronic system where leakage current andswitching noise can be converted to DC output;

FIG. 2 shows a prior art circuit for providing two levels of DC outputreferenced to secondary ground;

FIG. 3 shows an example prophetic plot of a potential difference betweena primary ground and a secondary ground;

FIG. 4 shows an example circuit for converting leakage current andswitching noise to DC output referenced to a secondary ground;

FIG. 5 shows an example plot of a potential difference between a primaryground and a secondary ground as well as output of a voltage source thatconverts leakage current and switching noise to DC output;

FIG. 6 shows an example circuit for converting leakage current andswitching noise to two levels of DC output referenced to a secondaryground;

FIG. 7 shows an example plot of a potential difference between a primaryground and a secondary ground as well as output of two voltage sourcesthat convert leakage current and switching noise to DC output;

FIG. 8 shows an example circuit for converting leakage current andswitching noise to two levels of DC output referenced to a primaryground; and

FIG. 9 shows an example method for converting leakage current andswitching noise to DC output.

DETAILED DESCRIPTION

The present description is related to converting leakage current andswitching noise to a regulated DC output voltage. In one example, twovoltage levels are provided to a system as is shown in FIG. 1 via aswitching power supply and a voltage regulation circuit such as is shownin FIG. 4. The first voltage is provided via a secondary coil of theswitching power supply, and the second voltage is provided via anelectrical potential difference between a primary ground and a secondaryground. FIGS. 6 and 8 illustrate alternative examples for providingsecond and third voltages via an electrical potential difference betweenthe primary ground and the secondary ground. FIGS. 3, 5, and 7 showprophetic examples of an electrical potential difference between primaryand secondary grounds as well as regulated voltages converted fromleakage current and switching noise. A method for converting leakagecurrent and switching noise to DC output is shown in FIG. 9.

Referring now to FIG. 1, an example electronic system where leakagecurrent and switching noise can be converted to DC output is shown.Electronic system 100 may include a display 102 for providing visualinformation to an operator. Electronic system 100 may also include achassis 104 that houses a power supply and electronics powered by thepower supply. Electronic system 100 is also shown with optionalhand-held controller 106 for operator input to electronic system 100. Inone example, the system is a game console and components within chassis104 may execute instructions for video gaming. In other examples,electronic system 100 may include electronics for an appliance (e.g.,microwave oven), computer, or other consumer electronics. Further, insome examples, electronic system 100 may include electronics andexecutable code for commercial applications such as computers,oscilloscopes, and instrumentation. The electronics of display 102,chassis 104, and hand-held controller 106 of electronic system 100 mayoperate with a plurality of voltage levels. For example, amicrocontroller of electronic system 100 may operate at a first voltagewhile a power control switch may operate at a second voltage.

Referring now to FIG. 2, a prior art circuit for providing two levels ofDC output referenced to secondary ground is shown. Electrical system 200includes power supply 202 for adjusting an AC input voltage into a lowerlevel system voltage (e.g., 5 volts). AC is input to power supply 202via terminals 290 and 292. AC is rectified to DC via full wave rectifier204. A DC voltage is output from full wave rectifier 204, filtered bybulk capacitor 254, and is electrically coupled to transformer 206. Inparticular, the DC voltage is electrically coupled to one side ofprimary coil 208. The other side of primary coil 208 is electricallycoupled to switching transistor 214. Switching transistor 214 is alsocoupled to primary ground 280. The duty cycle (e.g., ratio of on time tooff time) that switching transistor 214 is switched is controlled byisolation and pulse width modulation circuitry 216. Power is stored inthe primary coil 208 and transferred to secondary coil 212 and auxiliarycoil 210. Y capacitors 250, 252, and 218 reduce electromagneticinterference and are electrically coupled to the AC input lines, primaryground 280, and secondary ground 282.

Secondary coil 212 outputs a system voltage (e.g., a voltage that isused to power at least a portion of the electronics within electricalsystem 200) that is made available to system electronics when fieldeffect transistor (FET) 222 is activated (e.g., turned on by applying avoltage to the gate of FET 222). The output of secondary coil 212 is alower voltage (e.g., 5 volts) that is rectified by Schottky diode 258and filtered by bulk capacitor 266. FET 222 can be activated by a highervoltage (e.g., 15 volts) from auxiliary coil 210. The output ofauxiliary coil 210 is rectified by Schottky diode 256, filtered by bulkcapacitor 260 and ceramic capacitor 262, and then regulated via zenerdiode 264. The voltage from auxiliary coil 210 may activate FET 222 whenpush button switch 220 is activated by an operator.

Thus, in order to provide two voltages referenced to the secondaryground 282, the prior art circuit requires an auxiliary coil andrectification and filtering circuitry. The auxiliary coil increasessystem cost and weight. The auxiliary coil can also reduce theelectrical system efficiency because of losses related to transferringelectrical energy from the primary coil to the auxiliary coil.

Referring now to FIG. 3, an example prophetic plot of an electricalpotential difference between a primary ground and a secondary ground isshown. In particular, signal 302 represents an electrical potentialdifference between a primary ground and a secondary ground. The Y axisrepresents a voltage level while the X axis represents time. A voltagelevel above the X axis is positive while a voltage level below the Xaxis is negative. Thus, FIG. 3 shows that the electrical potentialdifference between a primary ground and a secondary ground varies inamplitude and time.

In one example, an electrical potential difference similar to signal 302occurs in a system where alternating current (AC) is rectified to DC,and the DC is input to a coil (e.g., primary coil) on the primary sideof a power supply transformer. The coil is switched to the primaryground to provide an output at the secondary coil of the transformer.The output from secondary coil is rectified into DC. The primary groundis a ground on the primary side of a transformer that adjusts an inputvoltage to a system level voltage at the secondary coil of thetransformer. The primary coil of the transformer may be referenced andswitched to the primary ground to operate the transformer. The secondarycoil of the transformer is referenced to the secondary ground on thesecondary side of the transformer. The primary ground is electricallyisolated from the secondary ground. However, in some systems a Ycapacitor may be present between the primary and secondary grounds tosuppress electromagnetic interference. Signal 302 represents a voltageor electrical potential that can develop between the primary ground andthe secondary ground. The peak-to-peak voltage developed between theprimary and secondary grounds can be more than 50 volts peak-to-peak.

The electrical potential shown in FIG. 3 represents electrical potentialbetween the primary ground and the secondary ground that may result froma combination of leakage current and switching noise. The leakagecurrent may originate from semiconductors such as transistors anddiodes. Further, leakage current may originate from capacitors, theprinted circuit board, and the transformer. In some examples, leakagecurrent may result from materials not being ideal electrical insulators.In other examples, leakage current may result from a circuit couplingwith the magnetic field of the power supply transformer. Thus, it can beseen from FIG. 3 that an electrical potential difference can existbetween a primary ground and a secondary ground of a power supply. And,the electrical potential difference between the primary and secondarygrounds shown in FIG. 3 may be the basis for generating voltages thatare different than the output voltage of the transformer secondary coil.

FIGS. 4, 6, and 8 depict examples of example circuits for convertingleakage current and switching noise to DC output. It will be appreciatedthat like referenced characters designate identical or correspondingcomponents and units throughout the several examples.

Referring now to FIG. 4, an example circuit for converting leakagecurrent and switching noise to DC output referenced to a secondaryground is shown. The primary ground 480 is the ground on the primary(e.g., input) side of transformer 406. The primary ground 480 isdesignated with a fork like symbol. The secondary ground 482 is theground on the secondary (e.g., output) side of transformer 406. Thesecondary ground 482 is designated with a triangle symbol. The primaryand secondary grounds are isolated from each other except in thisexample Y capacitor 418 is positioned between the primary ground and thesecondary ground. Y capacitors 418, 420, and 422 may be used to reduceelectromagnetic interference.

Electrical system 400 includes power supply 402 for adjusting an ACinput voltage into a lower level system voltage (e.g., 5 volts). AC isinput to power supply 402 via terminals 460 and 462. AC line power iselectrically coupled to terminal 460 and AC neutral is coupled toterminal 462. AC is rectified to DC via full-wave rectifier 404. A DCvoltage is output from full wave rectifier 404 and is electricallycoupled to transformer 406 after the voltage is filtered by bulkcapacitor 424. In particular, the DC voltage is electrically coupled toone side of primary coil 408. The other side of primary coil 408 iselectrically coupled to switching transistor 414. Switching transistor414 is also coupled to primary ground 480. Switching transistor 414periodically conducts when activated (e.g., turned on by applying avoltage to the gate) and periodically acts as an open circuit when notactivated (e.g. turned off by removing a voltage from the gate). Theduty cycle (e.g., ratio of on time to off time) that switchingtransistor 414 is switched is controlled by isolation and pulse widthmodulation circuitry 416. In one example, the duty cycle output byisolation and pulse width modulation circuitry 416 is related to theload applied to the output of transformer 406. Power is stored in theprimary coil 408 via a magnetic field when the switch is activated. Themagnetic field collapses when the switching transistor 414 isdeactivated inducing current flow in secondary coil 410. The output ofcoil 410 is rectified by Schottky diode 448 and the output voltage atthe cathode of Schottky diode 448 is filtered by the bulk filtercapacitor 466. The output voltage is also in communication with orelectrically coupled to the feedback circuit of the pulse widthmodulation circuit 416

Secondary coil 410 outputs a system voltage (e.g., a voltage that isused to power at least a portion of the electronics within electricalsystem 400) that is made available to system electronics when fieldeffect transistor (FET) 452 is activated (e.g., turned on by applying avoltage to the gate of FET 452). The voltage output of secondary coil410 may vary from application to application. For example, in somesystems the output of power supply 402 is 5 volts DC. In other examples,the output of power supply 402 is 15 volts DC.

In the present example, FET 452 may be activated by supplying a secondlevel DC voltage to the gate of FET 452. The second level DC voltage isa different voltage level as compared to the voltage level output bysecondary coil 410 and the second level DC voltage must be higher thanthe voltage level output by the secondary coil 410 in order to turn “on”FET 452. For example, FET 452 can be activated or turned on by applying15 volts to the gate of FET 452. A voltage can be supplied to the gateof FET 452 via operator control 450. In one example, operator control450 is a push button switch. The push button switch may provideselective electrical continuity between a power source and the gate ofFET 452. Thus, operator control 450 is capable of selectively putting apower source in communication with the gate of FET 452.

Diode 430, zener diode 434, and capacitor 432 are electrically coupledto comprise a voltage regulation circuit whereby an electrical potentialdifference between primary ground 480 and secondary ground 482 isconverted into a regulated voltage referenced to secondary ground 482.Diode 430 allows current to flow from primary ground 480 through Ycapacitor 418 and to capacitor 432 when diode 430 is forward biased.Diode 430 blocks current flow from capacitor 432 through Y capacitor 418and to primary ground 480 when diode 430 is reverse biased. Capacitor432 stores charge, capacitor 432 also filters an output voltage takenfrom between diode 430 and capacitor 432. Zener diode 434 permitscurrent to flow from secondary ground 482 through Y capacitor 418 and toprimary ground 480 when zener diode 434 is forward biased. Zener diode434 limits current flow from primary ground 480 through Y capacitor 418to secondary ground 482 at voltages less than the zener breakdownvoltage of zener diode 434 and when zener diode 434 is reverse biased.Zener diode 434 allows current flow from primary ground 480 through Ycapacitor 418 to secondary ground 482 when a voltage greater than thezener breakdown voltage of zener diode 434 is present and when zenerdiode 434 is reverse biased. Thus, zener diode 434 acts to regulate thevoltage of capacitor 432 to the zener breakdown voltage, and providesthe return path for negative leakage and noise voltage from secondaryground 482 to the primary ground 480 via Y capacitor 418.

An electrical potential difference between primary ground 480 andsecondary ground 482 may be the result of leakage current and switchingnoise produced by opening and closing switching transistor 414. In oneexample, the zener breakdown voltage can be selected at 15.0 volts, avoltage suitable to activate FET 452. However, different zener diodeswith different zener breakdown voltages can be selected to providedifferent output voltage levels. In this example, the 15 volt output isshown in communication with or electrically coupled to the operatorcontrol 450 for activating and deactivating FET 452.

The circuitry of FIG. 4 allows multiple voltage outputs of differentvoltage levels from a single switching power supply. Further, thecircuitry of FIG. 4 allows different voltages to be produced by powersupply 402 with a single secondary coil so that the weight and cost of atransformer auxiliary coil, capacitors, Schottky diode, and zener diodeused to power FET 452 may be avoided. Further still, since an additionalvoltage is produced from voltage related to switching noise and leakagecurrent, the additional voltage is provided with no loss of efficiencyof transformer 406. And, since Y capacitor 418 is in series withcapacitor 432 and since Y capacitor 418 is sized with a small amount ofcapacitance (e.g., 1.5 nF) relative to capacitor 432 (e.g., 0.1 uF),current flow from primary ground 480 to secondary ground 482 can belimited to less than 5 mA as like capacitor 432 is not in the circuit.

Referring now to FIG. 5, an example prophetic plot of a potentialdifference between a primary ground and a secondary ground as well asoutput of a voltage source that converts leakage current and switchingnoise to DC output is shown. In particular, the signals of FIG. 5 arerepresentative for the electrical circuit of FIG. 4. Signal 502represents an electrical potential difference between a primary ground480 and a secondary ground 482 for the circuit of FIG. 4. Signal 504represents output of a voltage source (e.g., elements 430, 432, and 434of FIG. 4) that converts leakage current and switching noise to DCoutput. The Y axis represents a voltage level while the X axisrepresents time. A voltage level above the X axis is positive while avoltage level below the X axis is negative. Thus, FIG. 5 like FIG. 3shows that the electrical potential difference between a primary groundand a secondary ground varies in amplitude and time.

In this example, signal 504 is taken between capacitor 432 and diode 430from the circuit shown in FIG. 4. Signal 502 and signal 504 are shown atdifferent scale and are not shown for voltage level comparisons, but arerather illustrated to show that signal 504 can be produced from thevoltage of signal 502.

Referring now to FIG. 6, an example circuit for converting leakagecurrent and switching noise to two levels of DC output referenced to asecondary ground is shown. The elements of FIG. 6 that have the samenumerical identifiers as the elements of FIG. 4 operate the same as theelements described in FIG. 4. Accordingly, for the sake of brevity, thedescription of elements already described in FIG. 4 is omitted, but theelements of FIG. 6 having the same numerical identifiers as the elementsin FIG. 4 are to be understood to be the same in structure andoperation.

Diode 630, diode 632, zener diode 634, zener diode 640, capacitor 636,and capacitor 638 are electrically coupled to comprise a two outputvoltage regulation circuit whereby an electrical potential differencebetween primary ground 480 and secondary ground 482 is converted intotwo regulated voltages referenced to secondary ground 482. The firstoutput voltage is available between diode 630 and capacitor 638. Thesecond output voltage is available between diode 632 and capacitor 636.

Diode 630 allows current to flow from primary ground 480 through Ycapacitor 418 and to capacitor 638 and zener diode 640 when diode 630 isforward biased. Diode 630 blocks current flow from capacitor 638 andzener diode 640 through Y capacitor 418 and to primary ground 480 whendiode 630 is reverse biased. Capacitor 638 stores positive chargerelative to secondary ground 482, capacitor 638 also filters an outputvoltage taken from between diode 630 and capacitor 638. Zener diode 640limits current flow from primary ground 480 through Y capacitor 418 anddiode 630 when zener diode 640 is reverse biased at voltages less thanthe zener breakdown voltage of zener diode 640. But, since zener diode640 is in parallel with capacitor 638, capacitor 638 can charge whenprimary ground 480 is at a higher electrical potential than secondaryground 482 and when the voltage across zener diode 640 is less than thezener breakdown voltage of zener diode 640. Zener diode 640 allowscurrent flow from primary ground 480 through Y capacitor 418 tosecondary ground 482 across capacitor 638 when a voltage greater thanthe zener breakdown voltage of zener diode 640 is present acrosscapacitor 638 and when zener diode 640 is reverse biased. Thus, zenerdiode 640 acts to regulate the voltage of capacitor 638 to the zenerbreakdown voltage of zener diode 640. In this way, the first regulatedDC output positive voltage referenced to secondary ground 482 isproduced from leakage current and switching noise.

Diode 632 allows current to flow from secondary ground 482 throughcapacitor 636, zener diode 634 (provided the zener breakdown voltage isexceeded), and through Y capacitor 418 to primary ground 480 when diode632 is forward biased. Diode 632 blocks current flow from primary ground480 through Y capacitor 418, zener diode 634, and capacitor 636 tosecondary ground 482 when diode 632 is reverse biased. Capacitor 636stores negative charge relative to secondary ground 482, capacitor 636also filters an output voltage taken from between diode 632 andcapacitor 636. Zener diode 634 permits current to flow from secondaryground 482 to diode 632, Y capacitor 418, and on to primary ground 480when a voltage greater than the zener breakdown voltage of zener diode634 is present across capacitor 636. Thus, zener diode 634 acts toregulate the voltage of capacitor 636 to the zener breakdown voltage.Further, zener diode 634 is biased opposite of the zener diode 640 withrespect to the secondary ground. In this way, the second regulated DCoutput negative voltage referenced to secondary ground 482 is producedfrom leakage current and switching noise.

In this way, current may flow in a first current path through diode 630or in a second current path through diode 632. The two current pathsallow capacitors 638 and 636 to be charged so that two voltages areavailable from the electrical potential difference between primaryground 480 and secondary ground 482.

Thus, according to the circuit illustrated in FIG. 6, a plurality ofregulated voltages referenced to a secondary ground can be provided by avoltage regulation circuit that converts leakage current and switchingnoise to DC. Further, at least one regulated voltage converted fromleakage current and switching noise may be a positive voltage withrespect to the secondary ground. Further still, at least one regulatedvoltage converted from leakage current and switching noise may be anegative voltage with respect to the secondary ground.

Referring now to FIG. 7, an example prophetic plot of a potentialdifference between a primary ground and a secondary ground as well asoutput of a voltage source that converts leakage current and switchingnoise to two levels of DC output is shown. In particular, the signals ofFIG. 7 are representative for the electrical circuit of FIG. 6. Inparticular, signal 702 represents an electrical potential differencebetween a primary ground 480 and a secondary ground 482 for the circuitof FIG. 6. Signal 704 represents a positive output of a voltage source(e.g., elements 630, 638, and 640 of FIG. 6) with respect to secondaryground 482 that converts leakage current and switching noise to DCoutput. The Y axis represents a voltage level while the X axisrepresents time. A voltage level above the X axis is positive while avoltage level below the X axis is negative. Thus, FIG. 7 like FIG. 3shows that the electrical potential difference between a primary groundand a secondary ground varies in amplitude and time.

Signal 704 is taken between capacitor 638 and diode 630 from the circuitshown in FIG. 6. Signal 706 represents a negative output of a voltagesource (e.g., elements 632, 634, and 636 of FIG. 6) with respect tosecondary ground 482 that converts leakage current and switching noiseto DC output. In this example, signal 706 is taken between capacitor 636and diode 632 from the circuit shown in FIG. 6. Signals 702, 704, and706 are shown at different scale and are not shown for voltage levelcomparisons, but are rather illustrated to show that signals 704 and 706can be produced from the voltage of signal 702.

Referring now to FIG. 8, an example circuit for converting leakagecurrent and switching noise to two levels of DC output referenced to aprimary ground is shown. The elements of FIG. 8 that have the samenumerical identifiers as the elements of FIG. 4 operate the same as theelements described in FIG. 4. Accordingly, for the sake of brevity, thedescription of elements already described in FIG. 4 is omitted, but theelements of FIG. 8 having the same numerical identifiers as the elementsin FIG. 4 are to be understood to be the same in structure andoperation.

Diode 830, diode 840, zener diode 834, zener diode 838, capacitor 836,and capacitor 832 are electrically coupled to comprise a two outputvoltage regulation circuit whereby an electrical potential differencebetween primary ground 480 and secondary ground 482 is converted intotwo regulated voltages referenced to primary ground 480. The firstoutput voltage is available between diode 830 and capacitor 836. Thesecond output voltage is available between diode 840 and capacitor 832.

Diode 830 allows current to flow from secondary ground 482 through Ycapacitor 818 and to capacitor 836 and zener diode 834 when diode 830 isforward bias. Diode 830 blocks current flow from capacitor 836 and zenerdiode 834 through Y capacitor 818 and to secondary ground 482 when diode830 is reverse biased. Capacitor 836 stores positive charge relative toprimary ground 480, capacitor 836 also filters an output voltage takenfrom between diode 830 and capacitor 836. Zener diode 834 permitscurrent flow from secondary ground 482 through Y capacitor 818 and diode830 when zener diode 834 is reversed biased at voltages less than thezener breakdown voltage of zener diode 834. But, since zener diode 834is in parallel with capacitor 836, capacitor 836 can charge whensecondary ground 482 is at a higher electrical potential than primaryground 480 and when the voltage across zener diode 834 is less than thezener breakdown voltage of zener diode 834. Zener diode 834 allowscurrent flow from secondary ground 482 through Y capacitor 818 toprimary ground 480 around capacitor 836 when a voltage greater than thezener breakdown voltage of zener diode 834 is present across capacitor836 and when zener diode 834 is reverse biased. Thus, zener diode 834acts to regulate the voltage of capacitor 836 to the zener breakdownvoltage of zener diode 834. In this way, the first DC output positivevoltage referenced to the primary ground 480 is produced from leakagecurrent and switching noise.

Diode 840 allows current to flow from primary ground 480 throughcapacitor 832, zener diode 838 (provided the zener breakdown voltage isexceeded), and through Y capacitor 818 to secondary ground 482 whendiode 840 is forward biased. Diode 840 blocks current flow fromsecondary ground 482 through Y capacitor 818, zener diode 838, andcapacitor 832 to primary ground 480 when diode 840 is reverse biased.Capacitor 832 stores negative charge relative to primary ground 480,capacitor 832 also filters an output voltage taken from between diode840 and capacitor 832. Zener diode 838 permits current to flow fromprimary ground 480 to diode 840, Y capacitor 818, and on to secondaryground 482 when zener diode 838 is reverse biased and when a voltagegreater than the zener breakdown voltage of zener diode 838 is presentacross capacitor 832. Thus, zener diode 838 acts to regulate the voltageof capacitor 832 to the zener breakdown voltage of zener diode 838. Inthis way, a second DC output negative voltage referenced to primaryground 480 is produced from leakage current and switching noise.

In this way, current may flow in a first current path through diode 830or in a second current path through diode 840. The two current pathsallow capacitors 836 and 832 to be charged so that two voltages areavailable from the electrical potential difference between primaryground 480 and secondary ground 482.

Thus, according to the circuit illustrated in FIG. 8, a plurality ofregulated voltages referenced to a primary ground can be provided by avoltage regulation circuit that converts leakage current and switchingnoise to DC. Further, at least one regulated voltage converted fromleakage current and switching noise may be a positive voltage withrespect to primary ground 480. Further still, at least one regulatedvoltage converted from leakage current and switching noise may be anegative voltage with respect to primary ground 480.

Referring now to FIG. 9, a method for converting leakage current andswitching noise to DC output is shown. The method of FIG. 9 isapplicable to the circuits of FIGS. 4, 6, and 8 as well as otheranticipated circuit variations.

At 902, method 900 supplies a voltage to an input of a transformer. Forexample, a voltage is supplied between input terminal 460 and inputterminal 462 of FIG. 4. In some examples, an AC input may be rectifiedbefore being applied to a primary side coil of a transformer. In otherexamples, a DC input may be applied to the primary side coil of atransformer. Method 900 proceeds to 904 after a voltage is applied to atransformer.

At 904, the primary coil of the transformer is switched to a primaryground on the primary side of the transformer. The transformer may beswitched to the primary ground via a FET, bi-polar, MOSFET, or otherknown type of transistor. The transistor may be switched at a varyingfrequency or a varying pulse width. For example, as shown in the circuitof FIG. 4, switching transistor 414 switches primary coil 408 oftransformer 406 to primary ground 480. Method 900 proceeds to 906 aftertransformer switching begins.

At 906, method 900 outputs a voltage from the secondary coil of theswitched transformer. When the primary coil of the transformer isswitched on, the primary coil is coupled to the primary ground therebyproducing a magnetic field that stores energy within the transformer.When the primary coil of the transformer is switched off, the primarycoil is uncoupled from the primary ground and the magnetic fieldcollapses inducing current flow in the secondary coil of thetransformer. The induced current provides a voltage at the secondarycoil of the transformer which is output from the transformer. Method 900proceeds to 908 after the transformer begins to output a voltage.

At 908, method 900 produces a regulated second voltage output fromconverting leakage current and switching noise that create an electricalpotential difference between a primary ground and a secondary ground.The primary ground is on the primary side of the transformer while thesecondary ground is on the secondary side of the transformer. Theprimary ground and the secondary grounds may be electrically isolatedfrom each other. Further, in some examples a Y capacitor may be placedbetween the primary and secondary grounds. In one example, the regulatedsecond voltage is output from the circuit of FIG. 4. In other examples,a plurality of voltages with different polarities and referenced to thesecondary ground or the primary ground may be provided according to thecircuits of FIGS. 6 and 8. Thus, the regulated voltages may bereferenced to primary or secondary grounds. Method 900 proceeds to 910after converting leakage current and switching noise to a regulated DCoutput.

At 910, method 900 judges whether or not to output voltage from thesecondary coil of the transformer to an electrical load of a system. Inone example, method outputs voltage from the secondary coil of thetransformer to the electrical load in response to an operator input(e.g., a push button input). If power to the system is requested by theoperator, method 900 proceeds to 912. Otherwise, method 900 proceeds toexit and power from the transformer secondary coil is not output to thesystem electrical load.

At 912, method 900 activates a transistor with the second voltage thatis produced by converting leakage current and switching noise to a DCoutput. Activating the transistor couples the output of the transformersecondary coil to the system electrical load. In one example, thetransistor is a FET and the FET begins to conduct when a positivevoltage that is higher than the output secondary voltage with respect tothe secondary ground is applied to the gate of the FET. For example,voltage from between diode 430 and capacitor 432 of FIG. 4 is applied tothe gate of FET 452. When the second voltage is applied to the FET, theFET begins to conduct. In this way, a second voltage at a second voltagelevel, the second voltage produced by converting leakage current andswitching noise to DC, activates a FET to couple a first voltage outputfrom a transformer secondary coil to a system electrical load inresponse to an operator input. Method 900 proceeds to exit afteroutputting the voltage of the transformer secondary coil.

By making use of an electrical potential difference between a primaryground and a secondary ground of a power supply, a second voltage sourcecan be provided. In one example, the second voltage source obtains powerfrom leakage currents and switching noise. Thus, power that mayotherwise directed to ground to reduce electrical noise is convertedinto a second voltage source that may be utilized by system componentsthat operate at a different voltage level than the voltage level outputby a power supply transformer.

The present description may provide several advantages. In particular,the approach can reduce power consumption since the second voltagesource makes use of leakage current and switching noise rather thandrawing directly from the secondary coil of the power supplytransformer. Further, the approach can reduce system cost and weightbecause the second voltage is not produced by an auxiliary transformercoil.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated may beperformed in the sequence illustrated, in other sequences, in parallel,or in some cases omitted. Likewise, the order of the above-describedprocesses may be changed.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

The invention claimed is:
 1. A power converter comprising: a transformercomprising: a primary coil having in selective electrical communicationwith a primary ground; and a secondary coil in electrical communicationwith a secondary ground, the secondary ground different than the primaryground, the secondary coil configured to provide a first voltage; atransistor comprising: a first terminal in selective electricalcommunication with a first terminal voltage, the first terminal voltagebased on the first voltage; a second terminal in electricalcommunication with a regulated voltage, the regulated voltage based onan electrical potential difference between the primary ground and thesecondary ground; and a diode and a capacitor positioned in anelectrical path between the primary ground and the secondary ground. 2.The power converter of claim 1, further comprising a rectifierpositioned between the secondary coil and the first terminal, therectifier rectifying the first voltage to provide the first terminalvoltage.
 3. The power converter of claim 2, wherein the rectifiercomprises a second diode.
 4. The power converter of claim 2, furthercomprising a filter configured to filter the first terminal voltage. 5.The power converter of claim 4, wherein the filter comprises acapacitor.
 6. A power converter comprising: an alternating current inputterminal; a rectifier coupled to the alternating current input terminal;a transformer coupled to the rectifier, the transformer comprising: aprimary coil in electrical communication with a primary ground; and asecondary coil in electrical communication with a secondary ground, thesecondary ground electrically isolated from the primary ground; and avoltage regulation circuit in series with a Y capacitor, the voltageregulation circuit and the Y capacitor positioned between andelectrically coupled to the primary ground and the secondary ground. 7.The power converter of claim 6, where the Y capacitor is electricallycoupled to the secondary ground via a zener diode.
 8. The powerconverter of claim 7, further comprising a diode positioned electricallyin parallel with the zener diode.
 9. The power converter of claim 8,further comprising a filter capacitor positioned electrically in serieswith the diode and electrically in parallel with the zener diode. 10.The power converter of claim 9, where the filter capacitor iselectrically coupled to a switch.
 11. The power converter of claim 10,where the switch is electrically coupled to a transistor, and where thetransistor selectively outputs a voltage based on an output voltage ofthe secondary coil.
 12. The power converter of claim 6, where the Ycapacitor is electrically coupled to an anode of a first diode and acathode of a second diode.
 13. The power converter of claim 12, wherethe first diode is electrically coupled to a first capacitor, where thesecond diode is electrically coupled to a second capacitor, and wherethe first and second capacitors are electrically coupled to thesecondary ground.
 14. A method for supplying primary and secondary powersources, comprising: producing a first voltage based on the output of atransformer, the transformer having a primary ground and a secondaryground; and producing a regulated second voltage via an electricalpotential difference between the primary ground and the secondaryground, where the first voltage is electrically coupled and decoupledfrom an electrical load via a transistor that is activated anddeactivated via the regulated second voltage.
 15. The method of claim14, where the regulated second voltage is supplied to a switch.
 16. Themethod of claim 15, where the regulated second voltage is supplied tothe transistor via the switch.
 17. The method of claim 14, where theregulated second voltage is based on an output of a zener diode.
 18. Themethod of claim 17, where the regulated second voltage is filtered via acapacitor.